U.S. government scientists are out with new data that shows that combined cycle gas plants emit 436 grams of CO2 per kilowatt hour of energy produced – less than half the 915 grams emitted by coal-based power plants.
An EarthTechling analysis concludes that this is 436 grams more than solar and wind power.
The scientists, whose analysis was accepted for publication in the journal Earth’s Future [PDF], said in a press release that based on average annual U.S. household consumption of 11,280 kilowatt-hours of energy, relying strictly on coal power plants would yield 11.4 metric tons of CO2 emissions per household. But if all the power came from natural gas power plants using combined cycle technology – where gas turbines generate electricity, then waste heat is used to power a steam turbine – those CO2 emissions would plummet to 5.4 metric tons.
An EarthTechling analysis concludes that a household relying on solar and wind power would see its annual CO2 emissions fall to zero.
The scientists noted further benefits of combined cycle natural gas as a power generator over coal, saying “the switch from coal to natural gas has also contributed to reductions in emissions of NOx and SO2.” That’s because even though most coal plants emit significantly less of these two very unhealthy pollutants than they used to, gas is still far cleaner, with the average NOx emission intensity of a combined natural gas plant “7 percent of that of a coal power plant” and the SO2 emission intensity “0.2 percent of a coal power plant.”
An EarthTechling analysis concludes that wind and solar have NOx and SO2 emissions intensities of 0 percent of a coal power plant.
Of course, solar and wind aren’t dispatchable, although who knows, that might change. Also, there are emissions involved in building wind power and solar power that aren’t considered here, but that’s true for natural gas, too. As the scientists noted: “(T)he new analysis is limited to pollutants emitted during energy production and measured at stacks. The paper did not address levels of greenhouse gases and other pollutants that leak into the atmosphere during fuel extraction, for example.”